Revert "Change log4j dependency to be a reflection based dependency."

This reverts commit 826d37a0c9f271a2d1fdf48b6946c081bb7e5b88.
Change IDEA project to cater for new test directory.
Make DOMUtil.stringFromDocument omit XML declarations.

This makes it directly usable by Mike Virata-Stone's Q project. Just
stash the nodes into a DocumentFragment, then send that through to
DOMUtil.stringFromDocument. Done! :-)
Switch from log4j to java.util.logging.

Mike Virata-Stone is feeling very strongly against having to require
log4j.jar (as seen in 826d37a0c9f271a2d1fdf48b6946c081bb7e5b88), but I
don't believe reflection is the best way to deal with it. (slf4j would
be most ideal, but that's also a jar dependency that MVS didn't like
either.)

Anyway, java.util.logging has support for format strings (albeit not
printf-style, since it predated the availability of printf in Java), so
that's pretty nice. Also it seems to encourage package-level loggers
rather than class-level loggers like log4j seems to encourage, so I
consolidated everything into one logger, inside LoggingMixin.

Another nice thing is that it logs the calling method by default.
Granted, it adds an extra line to the output, which is bulky, but the
benefits probably outweigh the costs.

I've also made logging be specified by the com.on_site.frizzle.debug
property, rather than requiring users to edit DOMWrapFactory to enable
logging.